<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script src="https://cdn.jsdelivr.net/npm/vue"></script>
</head>
<body>
<div id="app1">
    <p v-if="seen">我是看见的</p>
</div>
</body>
</html>
<script>
    var app1=new Vue({
        el:'#app1',
        data:{
            seen:true
        }
    });

    /**
     * 运行流程
     * 1. 绑定元素id
     * 2. new Vue
     * 3. el绑定app
     * 4. data赋值
     */
</script>